Delta del Ebro
After travelling across Castilla-Leon, Pais Vasco, La Rioja, Navarra, Aragon and Catalonia, and Mirando de Ebro, Haro, Logroño, Tudela, Zaragoza and Tortosa, the River Ebro finally reaches the Mediterranean where it fans out to form the Delta de Ebro covering 320 km², one of the most important wetlands in Europe . Although the existence of the Delta is a natural phenomenon, much of its current shape and extent is man-induced from upstream deforestation and overgrazing of the sierras of its huge catchment area, particularly as the river passed through Aragon . In the 4th century C.E. for example the Roman town of Amposta was port with a seafront (see map). The process was interrupted in the mid-twentieth century when dam-building (Ebro, Mequinenza and Ribarroja) began to block the provision of sediments. In recent years, the Delta has begun to recede and is thought to be particularly at threat from hypothetical sea-level rises over the next century. The threat is double: one from sea level rise; and two and probably currently more of a danger from sinking without the constant top-up of sediments from upstream. Intensive rice farming covers 60% of the delta.
Despite having the greatest discharge of any Spanish river, irrigation is responsible for a significant hydrological deficit: an average of 300 m3/s is taken off the river, reducing average natural flow from 745 m3/s to 430. Although the PNH (a plan to deliver much of the river’s water south) has been shelved, the revealing of large deposits of heavy metal and radioactive waste at the Flix reservoir, has cast a new shadow on the river’s and delta’s future.
The Ebro Delta is a Natural Park. Parts of the area are also designated as Natural Reserves (Illa de Sapinya 4ha and Punta de la Banya 2,500 ha), and National Hunting Refuges (Laguna de l’Encanyissada and Laguna de la Tancada).
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Information below adapted from Ramsar Directory of Wetlands of International Importance (1992)
CataloniaImportance: The Ebro Delta is a typical example of a fluvial delta. Some 30,000 pairs of waterbirds nest annually, while mid-winter waterbird counts have recorded 180,000 individuals. Breeding species include Ardea purpurea , Egretta garzetta , Bubulcus ibis , Ardeola ralloides , Nycticorax nycticorax , Ixobrychus minutus , Botaurus stellaris , Netta rufina , Himantopus himantopus , Glareola pratincola , Larus audouinii (with 7,000 pairs in 1992, the largest colony in the world), Chlidonias hybridus, Gelochelidon nilotica, Sterna albifrons , Sterna hirundo and S. sandvicensis . In summer, up to 4,000 non-breeding Phoenicopterus ruber roseus occur. Thousands of Egretta garzetta and Bubulcus ibis winter, as well as duck species, such as Anas platyrhynchos (42,800 in 1989), A. strepera (4,119 in 1985), A. clypeata (14,200 in 1991) and Netta rufina (6,100 in 1991), and up to 32,000 shorebirds (e.g. Recurvirostra avosetta and Limosa limosa ).
Wetland Types: The site is a fluvial delta, including a variety of wetlands, amongst which are shallow coastal waters, sandy beaches and dunes, saline lagoons, salinas, freshwater marshes, and freshwater pools fed by groundwater springs. At the end of the 19th Century, the introduction of agriculture transformed most of the delta so that rice fields, covering more than 20,000 ha, now dominate the region. The primary natural wetland types are permanent rivers and estuarine habitats.
Biological/Ecological notes: The shallow offshore waters around the delta are extremely important as spawning and nursery areas for fish, including many commercially valuable species. Four of the delta’s fish species are endemic to the Iberian Peninsula (e.g. Aphanius iberus ). The delta also supports an outstanding mollusc fauna (marine and freshwater), while the saltwater channels hold a small endemic shrimp Palaemonetes zariqueyi . In addition to typical Mediterranean plant communities, some plant species reach their northern limit in the delta ( Lonicera biflora, Tamarix boveana and Zygophyllum album ), while for others this is their southernmost locality ( Nymphaea alba, Alnus glutinosa ).
Hydrological/Physical notes: The delta’s flooding regime is now artificially regulated for rice cultivation. During the winter (November to April) low water levels are maintained, and inflow of seawater occurs. Conversely, during summer, fresh water is fed into the delta from the river, through a network of artificial channels, and high levels are maintained until October. The inundated area shrinks to a minimum between February and April.
Human Uses: Much of the Natural Park (including virtually all of the littoral zones) is in public ownership, although some of the major lagoons are privately owned. The principal land uses within the site are hunting, fishing, shellfish harvesting, tourism and limited agriculture, aquaculture and livestock rearing.
Adverse Factors: The water in the delta is highly contaminated by agricultural chemicals and some of the lagoons (Encanyissada, Olles, Platjola) are in an advanced state of eutrophication. Other reported problems within the site include over-exploitation of natural resources (through hunting, fishing, shellfish harvesting etc.) and insufficiently regulated tourism/recreation. Dam construction in the delta’s catchment has resulted in a significant decrease in the volume of sediment reaching the wetland, leading in turn to shrinkage of the delta by as much as 75 m per year in some of the most important areas (e.g. Isla de Buda, Punta de la Banya).
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